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Message-ID: <20150210102542.GC9505@redhat.com> Date: Tue, 10 Feb 2015 11:25:42 +0100 From: "Michael S. Tsirkin" <mst@...hat.com> To: Jason Wang <jasowang@...hat.com> Cc: Rusty Russell <rusty@...tcorp.com.au>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, pagupta@...hat.com Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support On Tue, Feb 10, 2015 at 06:59:30AM +0008, Jason Wang wrote: > > > On Tue, Feb 10, 2015 at 9:32 AM, Rusty Russell <rusty@...tcorp.com.au> > wrote: > >Jason Wang <jasowang@...hat.com> writes: > >> This patch enables the interrupt coalescing setting through ethtool. > > > >The problem is that there's nothing network specific about interrupt > >coalescing. I can see other devices wanting exactly the same thing, > >which means we'd deprecate this in the next virtio standard. > > > >I think the right answer is to extend like we did with > >vring_used_event(), eg: > > > >1) Add a new feature VIRTIO_F_RING_COALESCE. > >2) Add another a 32-bit field after vring_used_event(), eg: > > #define vring_used_delay(vr) (*(u32 *)((vr)->avail->ring[(vr)->num > >+ 2])) > > Yes. This looks better and we don't even need device specific configuration > method. > > > > >This loses the ability to coalesce by number of frames, but we can still > >do number of sg entries, as we do now with used_event, and we could > >change virtqueue_enable_cb_delayed() to take a precise number if we > >wanted. > > Can we give a device specific meaning for this? For virtio-net, we want to > expose the coalescing settings through ethtool (tx-frames). And it was > usually used with a timer, so probably another field after > vring_used_delay() for this timer interval to trigger the interrupt if no > new used buffers come after this interval. I think what Rusty has in mind is precisely sticking the delay in vring_used_delay. > > > > > >My feeling is that this should be a v1.0-only feature though > >(eg. feature bit 33). > > Yes it should. > > > > >Cheers, > >Rusty. > > > >> Cc: Rusty Russell <rusty@...tcorp.com.au> > >> Cc: Michael S. Tsirkin <mst@...hat.com> > >> Signed-off-by: Jason Wang <jasowang@...hat.com> > >> --- > >> drivers/net/virtio_net.c | 67 > >>+++++++++++++++++++++++++++++++++++++++++ > >> include/uapi/linux/virtio_net.h | 12 ++++++++ > >> 2 files changed, 79 insertions(+) > >> > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >> index cc5f5de..2b958fb 100644 > >> --- a/drivers/net/virtio_net.c > >> +++ b/drivers/net/virtio_net.c > >> @@ -145,6 +145,11 @@ struct virtnet_info { > >> /* Budget for polling tx completion */ > >> u32 tx_work_limit; > >> + > >> + __u32 rx_coalesce_usecs; > >> + __u32 rx_max_coalesced_frames; > >> + __u32 tx_coalesce_usecs; > >> + __u32 tx_max_coalesced_frames; > >> }; > >> struct padded_vnet_hdr { > >> @@ -1404,12 +1409,73 @@ static void virtnet_get_channels(struct > >>net_device *dev, > >> channels->other_count = 0; > >> } > >> +static int virtnet_set_coalesce(struct net_device *dev, > >> + struct ethtool_coalesce *ec) > >> +{ > >> + struct virtnet_info *vi = netdev_priv(dev); > >> + struct scatterlist sg; > >> + struct virtio_net_ctrl_coalesce c; > >> + > >> + if (!vi->has_cvq || > >> + !virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_COALESCE)) > >> + return -EOPNOTSUPP; > >> + if (vi->rx_coalesce_usecs != ec->rx_coalesce_usecs || > >> + vi->rx_max_coalesced_frames != ec->rx_max_coalesced_frames) { > >> + c.coalesce_usecs = ec->rx_coalesce_usecs; > >> + c.max_coalesced_frames = ec->rx_max_coalesced_frames; > >> + sg_init_one(&sg, &c, sizeof(c)); > >> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_COALESCE, > >> + VIRTIO_NET_CTRL_COALESCE_RX_SET, > >> + &sg)) { > >> + dev_warn(&dev->dev, "Fail to set rx coalescing\n"); > >> + return -EINVAL; > >> + } > >> + vi->rx_coalesce_usecs = ec->rx_coalesce_usecs; > >> + vi->rx_max_coalesced_frames = ec->rx_max_coalesced_frames; > >> + } > >> + > >> + if (vi->tx_coalesce_usecs != ec->tx_coalesce_usecs || > >> + vi->tx_max_coalesced_frames != ec->tx_max_coalesced_frames) { > >> + c.coalesce_usecs = ec->tx_coalesce_usecs; > >> + c.max_coalesced_frames = ec->tx_max_coalesced_frames; > >> + sg_init_one(&sg, &c, sizeof(c)); > >> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_COALESCE, > >> + VIRTIO_NET_CTRL_COALESCE_TX_SET, > >> + &sg)) { > >> + dev_warn(&dev->dev, "Fail to set tx coalescing\n"); > >> + return -EINVAL; > >> + } > >> + vi->tx_coalesce_usecs = ec->tx_coalesce_usecs; > >> + vi->tx_max_coalesced_frames = ec->tx_max_coalesced_frames; > >> + } > >> + > >> + vi->tx_work_limit = ec->tx_max_coalesced_frames_irq; > >> + > >> + return 0; > >> +} > >> + > >> +static int virtnet_get_coalesce(struct net_device *dev, > >> + struct ethtool_coalesce *ec) > >> +{ > >> + struct virtnet_info *vi = netdev_priv(dev); > >> + > >> + ec->rx_coalesce_usecs = vi->rx_coalesce_usecs; > >> + ec->rx_max_coalesced_frames = vi->rx_max_coalesced_frames; > >> + ec->tx_coalesce_usecs = vi->tx_coalesce_usecs; > >> + ec->tx_max_coalesced_frames = vi->tx_max_coalesced_frames; > >> + ec->tx_max_coalesced_frames_irq = vi->tx_work_limit; > >> + > >> + return 0; > >> +} > >> + > >> static const struct ethtool_ops virtnet_ethtool_ops = { > >> .get_drvinfo = virtnet_get_drvinfo, > >> .get_link = ethtool_op_get_link, > >> .get_ringparam = virtnet_get_ringparam, > >> .set_channels = virtnet_set_channels, > >> .get_channels = virtnet_get_channels, > >> + .set_coalesce = virtnet_set_coalesce, > >> + .get_coalesce = virtnet_get_coalesce, > >> }; > >> #define MIN_MTU 68 > >> @@ -2048,6 +2114,7 @@ static unsigned int features[] = { > >> VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, > >> VIRTIO_NET_F_CTRL_MAC_ADDR, > >> VIRTIO_F_ANY_LAYOUT, > >> + VIRTIO_NET_F_CTRL_COALESCE, > >> }; > >> static struct virtio_driver virtio_net_driver = { > >> diff --git a/include/uapi/linux/virtio_net.h > >>b/include/uapi/linux/virtio_net.h > >> index b5f1677..332009d 100644 > >> --- a/include/uapi/linux/virtio_net.h > >> +++ b/include/uapi/linux/virtio_net.h > >> @@ -34,6 +34,7 @@ > >> /* The feature bitmap for virtio net */ > >> #define VIRTIO_NET_F_CSUM 0 /* Host handles pkts w/ partial csum */ > >> #define VIRTIO_NET_F_GUEST_CSUM 1 /* Guest handles pkts w/ partial > >>csum */ > >> +#define VIRTIO_NET_F_CTRL_COALESCE 3 /* Set coalescing */ > >> #define VIRTIO_NET_F_MAC 5 /* Host has given MAC address. */ > >> #define VIRTIO_NET_F_GSO 6 /* Host handles pkts w/ any GSO type */ > >> #define VIRTIO_NET_F_GUEST_TSO4 7 /* Guest can handle TSOv4 in. */ > >> @@ -202,4 +203,15 @@ struct virtio_net_ctrl_mq { > >> #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN 1 > >> #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX 0x8000 > >> +struct virtio_net_ctrl_coalesce { > >> + __u32 coalesce_usecs; > >> + __u32 max_coalesced_frames; > >> +}; > >> + > >> +#define VIRTIO_NET_CTRL_COALESCE 6 > >> + #define VIRTIO_NET_CTRL_COALESCE_TX_SET 0 > >> + #define VIRTIO_NET_CTRL_COALESCE_TX_GET 1 > >> + #define VIRTIO_NET_CTRL_COALESCE_RX_SET 2 > >> + #define VIRTIO_NET_CTRL_COALESCE_RX_GET 3 > >> + > >> #endif /* _LINUX_VIRTIO_NET_H */ > >> -- 1.8.3.1 > >-- > >To unsubscribe from this list: send the line "unsubscribe netdev" in > >the body of a message to majordomo@...r.kernel.org > >More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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